Compared to a microtip field emission cathode, a thin film field emission flat cathode, such as a carbon thin film cathode, requires a simpler structure, and is easier and less expensive to manufacture. One of the challenges in producing a viable field emission flat cathode is the production of an addressable cathode because of two reasons. First, the emission properties of an emitting film often severely degrade when exposed to most processes. As a result, once the film is deposited, the cathode cannot be easily processed for patterning or other purposes. Second, there is often severe edge emission from cathode feedlines.
An addressable field emission flat cathode typically consists of metal feedlines on an insulating substrate and a field emitting film, such as an emitting carbon film, on top of the feedlines. The edges of these metal feedlines or the emitting material on these edges often emit electrons dominantly and preferentially over the desired area, such as the pixel area, because of an enhanced electrical field on these edges. As a result, the emission pattern is completely disrupted. The emission from the cathode becomes unpredictable and unstable.
Therefore, there is a need in the art for a flat field emission cathode, which has inhibited or eliminated edge emission from the metal and the emitting material located at metal feedline edges while maintaining strong emission from desired areas.